Rx Window as it appears at startup with an empty COMS plaque

The Prescription window unifies all prescription related functions. Controls are provided to set dose calculation options, the prescription point, date and time of plaque insertion and removal, and a customizable table of plaque Central AXis (CAX) or Tumor AXis (TAX) points which are automatically updated.

The plaque insertion and removal calendar controls are used to set the implant duration. The Implant Calculator button in the removal group simplifies calculation of required seed strength or implant duration.

The Rx Menu up on the MacOS menu bar provides additional control over Rx related functions and parameters.

  • Insertion controls group:
    • Calendar control - enter the prescribed insertion date and time. CalendarControl
    • Calendar41x41Calendar button - opens the interactive calendar sheet.
    • Today41x41Today button - sets the insertion date and time to the current date and time.

  • Removal controls group:
    • Duration - optionally enter the prescribed implant duration (in hours) in the text field.DurationField
    • Calendar control - enter the prescribed removal date and time.
    • Calendar button - opens the interactive calendar sheet.
    • Today button - sets the removal date and time to the current date and time.
    • Week55x411 Week button - sets the removal date and time to the insertion date and time plus 168 hours. Note: the duration applied by this button is a customizable preference setting, the button title will adapt to your preference.
    • ImplantCalcImplant calculator button - opens the implant calculator window in which you can calculate the duration and/or source strength required to achieve the prescription.

The Rx units button (with popup-menu) along the lower border controls the display units for the prescription.

UnitsMenu

The PS dosimetric model for gamma emitting sources is based on the AAPM TG43 methodology with modifiers to account for the inhomogeneous environment surrounding the radiation sources compared to infinite water. The buttons in the toolbar at the top of the window select which of the dose calculation options available to the PS model to use for different models of plaque.

  • Linear/Point - Select linear vs point source model (recommend linear).
  • Isotropy - Select isotropic vs anisotropic source model (recommend anisotropic).
  • Carrier - Enable and select a COMS silicone carrier correction method (enable only for COMS plaques).
  • Gold - Enable the PS gold flourescence modifier (disable for COMS plaques, enable for EP plaques).
  • Lipped/Slotted - Choose between lipped vs slotted plaque models. Ray-tracing the collimating effect of a rectangular slot in the face of the plaque that is very close to a source is much faster than ray-tracing the surrounding shell of the plaque. (Set to lipped for all COMS and ROPES plaques, slotted for EP plaques).
  • Shell - Enables shell collimation ray tracing. Ray tracing the shell is very fast for circular plaques and comparatively slow for noncircular plaques and any plaque with a notch. (Enable for all COMS and ROPES plaques, recommend to disable for EP plaques since nearly all collimation occurs at the slot opening).
  • Air - Enable the PS backscatter modifier to account for air in front of the cornea.
RxWindowAtStartup

The red background tint in the table is a warning that the calculated dose does not match the Rx. The yellow is a warning that the implant duration does not fall within the preferences limits. These tints will turn green when the Rx and duration conditions have been met.



Rx Window as it appears with a COMS plaque filled with seeds

These are the dose calculation parameter button settings for a COMS plaque with a silicone seed carrier. The COMS plaque has a shell with a lip.

  • PS Calculation enabled (vs the obsolete COMS protocol).
  • Linear source mode enabled (vs point source).
  • Anisotropy corrections enabled.
  • Silicone carrier corrections enabled.
  • Gold flourescence corrections disabled (flourescence is absorbed in the COMS carrier).
  • Air scatter corrections disabled.
  • Shell collimation enabled.
  • The seeds are only collimated by the lip (vs by individual slots).

The plaque is loaded with seeds so as to deliver 85Gy to the apex of a 4.5 mm tall equatorial tumor (note that tumor height is measured from the inner sclera) in 1 week (168 hours). Note: in this example, a change from standard time to daylight saving time occurs on Sunday March 9th, which happens to fall within the prescribed 168 hour implant. The removal time was automatically adjusted to 11 AM (for an implant time of 10 AM) to account for this clock change. The Rx units have been set to Gy. The dashed blue line indicates where the Rx dose falls in the table.

RxWindowCOMS

Rx Window as it appears with an Eye Physics plaque filled with seeds

These are the dose calculation parameter button settings for an Eye Physics plaque.

  • PS Calculation enabled (vs the obsolete COMS protocol).
  • Linear source mode enabled (vs point source).
  • Anisotropy corrections enabled.
  • Silicone carrier corrections disabled (Eye Physics plaques have no carrier).
  • Gold flourescence corrections enabled.
  • Air scatter corrections disabled.
  • Shell collimation disabled (redundant for a slotted plaque).
  • Slot collimation enabled.

The plaque is loaded with seeds so as to deliver 85Gy to the apex of a 4.5 mm tall equatorial tumor (note that tumor height is measured from the inner sclera) in 7 days (168 hours). Note: in this example, a change from standard time to daylight saving time occurs on Sunday March 9th, which happens to fall within the prescribed 168 hour implant. The removal time was automatically adjusted to 11 AM (for an implant time of 10 AM) to account for this clock change. The Rx units have been set to Gy. The dashed blue line indicates where the Rx dose falls in the table.

RxWindowEP

Changing the Rx point in the Rx Window

The Prescribe to menu sets the dose prescription point. This is generally the apex of the tumor for tumors > 5 mm height, and about 4 to 5 mm for shorter tumors in order to assure sufficient margin surrounding the tumor base.

RxWindowWithRxMenu

Customizing the Rx Window's axis table

Clicking the Customize button at the bottom of the window
CustomizeBtn

opens a dialog sheet in which you can configure the Central AXis table.

  • Axis controls group:
    • Select between a table of plaque Central AXis (CAX) or Tumor AXis (TAX) points.
    • Plaque: - Select which plaque to tabulate. By default this will be the plaque to which the Rx applies.
      AxisPlaqueMenu
    • Tumor: - Select which tumor to tabulate. By default this will be tumor #1.
      AxisPlaqueMenu
CustomizeDialogCAX
CustomizeDialogTAX
  • Zero controls group (CAX mode):
    • Plaque face: - Zero distance in the table corresponds to the plaque face. This is the default setting.
    • Plaque face + 1 mm: - Zero distance in the table corresponds to 1 mm in front of the plaque face, which in most cases will be the inner sclera.
  • Zero controls group (TAX mode):
    • External sclera below tumor: - Zero distance in the table corresponds to the external sclera below the geometric center of the tumor base. This is the default setting.
    • Inner sclera below tumor: - Zero distance in the table corresponds to the inner sclera at the geometric center of the tumor base.
  • Mode controls group:
    • 1 mm averaging: - Off by default. By enabling this checkbox, the table calculates the average dose over a 1 mm range surrounding the point instead of at a single coordinate point on the axis.
    • Normalize to index: - Normalizes the tabulated dosimetry to one of the 16 table distance indices (e.g. index 5 corresponds to a distance of 4.5 mm in this example). ModeNormalizeMenu
    • Reverse tumor axis direction: - Reverses the direction of the Tumor AXis. The standard tumor axis projects a line from the center of the tumor base towards the tumor apex. Reversing the tumor axis projects the line from the apex towards the base. This can be useful for tumors located in the space between the iris and the cornea.
  • BEBIG controls group:
    • 11 Points (0.6 to 10.0): - The current protocol.
    • 11 Points (0.7 to 10.7): - An older protocol.
    • 3 Points (2.0,3.5,5.0): - A very old protocol. BEBIGProtocolMenu
  • Distance controls group:
    • 0..15: Enter the distances along the plaque or tumor axis at which to calculate dose. Index 0 is always a distance of zero and corresponds to either the face of the plaque or 1 mm in front of the face according to the setting in the Zero controls group on the left.